Submission #1257942

#	Time	Username	Problem	Language	Result	Execution time	Memory
1257942		proofy	Bomb (IZhO17_bomb)	C++20	20 / 100	1095 ms	4680 KiB

bomb

#include <bits/stdc++.h>
using namespace std;
#define ll long long

const int N = 453;
int L[N][N], R[N][N], U[N][N], D[N][N], J[N], a[N][N], T[N], p;

int Q[N], l, r;

int main() {
	ios::sync_with_stdio(0);
	cin.tie(0);

    int n, m;
    cin >> n >> m;
    for (int i = 1; i <= n; i++)
        for (int j = 1; j <= m; j++) {
            char c;
            cin >> c;
            a[i][j] = c - '0';
        }

    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= m; j++) 
            L[i][j] = (a[i][j] ? L[i][j - 1] + 1 : 0);
        for (int j = m; j >= 1; --j)
            R[i][j] = (a[i][j] ? R[i][j + 1] + 1 : 0);
    }

    int X = 1e9;
    for (int j = 1; j <= m; j++) {
        for (int i = 1; i <= n; i++)
            U[i][j] = (a[i][j] ? U[i - 1][j] + 1 : 0);
        for (int i = n; i >= 1; --i)
            D[i][j] = (a[i][j] ? D[i + 1][j] + 1 : 0);

        for (int i = 1; i <= n; i++) if (a[i][j])
            X = min(X, U[i][j] + D[i][j] - 1);
    }

    for (int h = 1; h <= X; h++) {
        J[h] = 1e9;
        for (int j = 1; j <= m; j++) { // fix a column j
            
            // sliding window minimum of size h over T
            deque<int> dq_R, dq_L;
            for (int i = 1; i <= n; i++) {
                if (!a[i][j]) {
                    dq_R = deque<int>();
                    dq_L = deque<int>();
                    continue;
                }
                while (!dq_R.empty() && dq_R.front() <= i - h) dq_R.pop_front();
                while (!dq_L.empty() && dq_L.front() <= i - h) dq_L.pop_front();

                while (!dq_R.empty() && R[dq_R.back()][j] >= R[i][j]) dq_R.pop_back();
                while (!dq_L.empty() && L[dq_L.back()][j] >= L[i][j]) dq_L.pop_back();
                dq_R.push_back(i);
                dq_L.push_back(i);

                if (U[i][j] >= h - 1) J[h] = min(J[h], L[dq_L.front()][j] + R[dq_R.front()][j] - 1);
            }
        }
    }

    int ans = 0;
    for (int h = 1; h <= X; h++) ans = max(ans, h * J[h]);

    cout << ans << "\n";
}

• Subtask 1: 20 / 100